How do those compare, they seem like a good deal for a cheap single speed I have. Is this place legit?

If i remember correctly the experts have qr rear only and the pro have adapters available for different rear axles. Think the experts were like 100g heavier or something too, nothing overly significant. At $300 for a wheelset you're obviously not getting high poe and great bearings etc. But for a cheap beat the crap out of and not worry wheelset seems like it'd be a nice fit. Just be aware that its prob an alum freehub at this price range and your SS cog may chew the crap out of it if you're putting out some decent power.